#include <iostream>

/**
 * 交换两个数
 */
int main(){

    int a = 10;
    int b = 20;

    std::cout << "交换前：" << std::endl;
    std::cout << "a = " << a << std::endl;
    std::cout << "b = " << b << std::endl;

    int temp = a;
    a = b;
    b = temp;

    std::cout << "交换后：" << std::endl;
    std::cout << "a = " << a << std::endl;
    std::cout << "b = " << b << std::endl;

    return 0;
}